Download Java DATABASE CONNECTIVITY JDBC

JDBC
The JDBC (Java Database Connectivity)
API helps a Java program to access a
database in a standard way
 JDBC is a specification that tells the
database vendors how to write a driver
program to interface Java programs with
their database

JDBC
A Driver written according to this
standard is called the JDBC Driver
 All related classes and interfaces are
present in the java.sql package
 All JDBC Drivers implement the
interfaces of java.sql

Database interaction

The steps involved in a database
interaction are:
– Loading the specific driver
– Making a connection to the database
– Sending SQL statements to the database
– Processing the results
Statement


A statement object is used to send SQL statements to
a database.
Three kinds :
Statement
 Execute simple SQL without parameters
PreparedStatement
 Used for pre-compiled SQL statements with or
without parameters
CallableStatement
 Execute a call to a database stored procedure or
function
JDBC - classes and interfaces

DriverManager class  Manages all the JDBC Drivers that are
loaded in the memory
 Helps in dynamic loading of Drivers

Methods in DriverManager class  getConnection() : to establish a connection
to a database.
○ Connection getConnection(String url,
Properties info)
○ Connection getConnection(String url)
○ Connection getConnection(String url, String
userID, String password)
 registerDriver(java.sql.Driver)

The different methods of Connection
interface are:
 close() - closes the database connection
 createStatement() - creates an SQL
Statement object
 prepareStatement() - creates an SQL
PreparedStatement object.
(PreparedStatement objects are precompiled
SQL statements)
 prepareCall() - creates an SQL
CallableStatement object using an SQL
string. (CallableStatement objects are SQL
stored procedure call statements)

Statement interface - defines methods that are used to interact
with database via the execution of SQL statements.

The different methods are:
 executeQuery(String sql) - executes an SQL statement (SELECT) that
queries a database and returns a ResultSet object.
 executeUpdate(String sql) - executes an SQL statement
(INSERT,UPDATE,or DELETE) that updates the database and returns
an int, the row count associated with the SQL statement
 execute(String sql) - executes an SQL statement that is written as
String object
 getResultSet() - used to retrieve the ResultSet object

ResultSet Interface - maintains a pointer to a
row within the tabular results. The next() method
is used to successively step through the rows of
the tabular results.

The different methods are:
 getBoolean(int) - Get the value of a column in
the current row as a Java boolean.
 getByte(int) - Get the value of a column in the
current row as a Java byte.
 getDouble(int) - Get the value of a column in
the current row as a Java double.
 getInt(int) - Get the value of a column in the
current row as a Java int.
import java.sql.*;
class JDBCTest{
public static void main(String args[]) {
try{
Class.forName ("oracle.jdbc.driver.OracleDriver");
Connection connection =
DriverManager.getConnection("jdbc:oracle:thin:@DB,
IPaddress:port_no:host string",“uid",“password");
Statement statement = connection.createStatement();
ResultSet resultSet = statement.executeQuery ("select * from
Student");
while (resultSet.next()) {
System.out.println ( resultSet.getInt ("ClassNo"));
}
}
catch (Exception exception) {
System.out.println (exception)
}
}
}
PreparedStatement interface -- helps us
to work with precompiled SQL
statements
 Precompiled SQL statements are faster
than normal statements
 So, if a SQL statement is to be repeated, it
is better to use PreparedStatement
 Some values of the statement can be
represented by a ? character which can be
replaced later using setXXX method

import java.sql.*;
class PreparedStatementTest{
public static void main(String args[]) throws Exception{
try{
Class.forName("oracle.jdbc.driver.OracleDriver");
Connection connection =
DriverManager.getConnection(“url“, “UID", “password ");
PreparedStatement preparedStatement =
connection.prepareStatement("select * from
Emp where ename=?");
preparedStatement.setString(1, 7521);
ResultSet resultSet = preparedStatement.executeQuery();
while(resultSet.next()){
System.out.println(resultSet.getString("ename"));
}
}
catch(Exception exception){
System.out.println(exception);
}
}
}

CallableStatement interface -- helps us
to call stored procedures and functions
CallableStatement callableStatement =
connection.prepareCall(“execute proc ?”);
callableStatement.setInt(50);
callableStatement.execute();


The out parameters are to be registered
callableStatement.registerOutParameter(int
parameterIndex, int SQLType);
To get the value stored in the out parameter-callableStatement.getXXX(int parameterIndex);
Example - Calling a stored procedure named GetSalary. The
procedure queries on the Employee table and returns the salary
of an employee. It has one input parameter that takes the
EmpCode and an out parameter that returns the salary
CallableStatement callableStatement =
connection.("begin GetSalary(?,?); end;");
callableStatement.(1,29418);
// OUT parameters must be registered.
callableStatement.(2,Types.DOUBLE);
callableStatement.execute();
System.out.println("Salary : “ +callableStatement.getDouble(2));


ResultSetMetaData Interface - holds
information on the types and properties of the
columns in a ResultSet. Provides information
about the database as a whole. Constructed from
the Connection object
The different methods are:
 getColumnName()
 getColumnType()
 getColumnLabel(count)